I'm not sure if this applies to the phase 1 ECU's (as I use a laptop to deal with mine) but the typical reset procedure for Alfas is:
Disconnect batt for ~45 minutes then reconnect
Key to MAR position for 90 seconds.
Key back to the off position for 90 seconds but leave the key in
Start and let idle for 15 minutes without touching anything
Turn off and leave off for 10 minutes with key still in ignition.

I've confirmed on my phase 2 cars that the procedure works but never tried it on my phase 1.

 

Thanks buddy much appreciated

 

Thanks for this post...it's just saved me calling out the AA or similar! I purchased a 2003 GTV on Tuesday and drove the 200 miles back to where I'm from with no problems at all. Yesterday was pleasant here for a change so I scrubbed out the floor mats and carpet. No problem I thought, I'll leave the doors open whilst it dries. Locks the car up at teatime, after closing the doors and windows. Now this morning it wouldn't start. Turning over but not catching. I thought it more electrical than anything but wasn't sure if I had disturbed anything during my scrubbing out session. A quick look on here and hey presto! Car starts and runs perfectly on the first flick of the key! Will keep an eye on things to make sure it's not a coincidence but I suspect not. What I did notice that during the key 'manipulation' sequence the car activated the indicators, as though the hazard lights were on, at certain time intervals. I suspect this will have been the immobiliser re-initialising?
Still whatever it worked and I am pleased, lets see if it starts again tomorrow morning when I go to work! Thanks again for the post, good work on here as always!

 

The Phase 1 3.0 V6 have a throttle cable, the Phase 2 is a drive by wire electronic throttle body which needs a more involved reset "learning" procedure.